Over the past twenty years, the value of pedicle screw stabilization in enhancing fusion procedures of the lumbar spine has been proven unambiguously. Many systems have been introduced to achieve this, and presently, numerous systems exist for the placement of screws and connecting rod or plate systems as a component of a classic lumbar fusion procedure. Most of these systems require an “open” procedure involving an extensive incision of the skin, extensive detachment or “takedown” of the paravertebral muscles, and exposure of the bony elements. This involves a significant, complex surgical intervention with massive dissection of the paravertebral musculature. As a consequence, the classic lumbar fusion procedure is associated with significant morbidity, including blood loss, increased anesthesia time with its attendant complications, and increased risk of infection. Additionally, quite often the patient experiences significant postoperative pain requiring a longer hospital stay which adds substantial cost to the current systems.
One of these procedures developed to overcome the drawbacks of the classic fusion procedure includes the use of unique endoscopic equipment. The cost of such equipment can be prohibitively high, which limits the use of this procedure to a few medical facilities. Still another undesirable consequence of the endoscopic procedure is its complexity, requiring considerable experience of a medical staff capable of using this equipment to properly place the screws as well as a staff of highly trained technicians.
U.S. Pat. No. 6,443,953 discloses the other, more commonly performed procedure associated with a system which is configured to interlock the pedicles of the vertebral bodies to be fused and includes inserting multiple screws into pedicles and bridging the screw heads of the screws by a connecting rod. As illustrated in FIGS. 1 and 2, implementation of such a procedure requires that a superior positioned incision be made in the paravertebral tissues of the lower thoracic area located below the lowest of the screws 22. Connecting rod 14 is then passed parallel to the spine, as indicated by an arrow A, through holes 18 in the screw heads 12 and is secured into position by initially topping the screw heads 12 with caps 20 and, further, by placing nuts 16 in the caps 20. Displacement of the rod 14 through soft tissues, otherwise uninvolved by the procedure, introduces potential injury to these soft tissues. Furthermore, this procedure requires the precise alignment of the screws and, particularly, each of the holes 18 of the adjacent screw heads 12 with the connecting rod 14 as well as with one another. Hence, the procedure is associated with additional requirements imposed upon a surgeon, an increase in overall surgery time and, as a consequence, additional health risks for the patient.
Yet another problem associated with the above discussed system is the issue of passing bone screws into the pedicles of the lumbar spine in such a fashion that with merely the use of surface anatomy, in conjunction with intraoperative imaging, the screws can be secured into the pedicles with maximum purchase of bone and minimum risk of injury to peri-pedicular structures, such as nerve roots.
It is, therefore, desirable to provide an instrumentation system and a method for using the same that minimize the disturbance of soft tissue, reduce the overall time of surgery, optimize the guidance of the connecting rod toward screws and simplify the placement of the rod and the screws.